Trachoma Transmission Research Articles

Impact of cattle on the prevalence and severity of trachoma.

Ethiopia is the African country with the largest number of cattle (26 million). Because of the potential impact of cattle on the transmission and severity of trachoma, the major cause of blindness in the country, an attempt is made to document this association to justify the inclusion of the control of cattle pollution in the prevention of blindness. The prevalence of trachoma is lower in pastoralists who herd mainly camels than in pastoralists who herd mainly cattle. In the first group the prevalences of moderate and severe trachoma in children under 10 are 0.9% and trichiasis/entropion in the total population 0.2%, whereas in the second group the prevalences are 45.1% and 4.0% respectively. In Borana pastoralists with and without cattle the prevalence ratio for moderate and severe trachoma is 1.0, whereas the prevalence ratios for severe trachoma and conjunctivitis were higher in the group with cattle, 2.5 and 3.0 (p less than 0.001 for both). The elimination of cattle pollution should reduce the prevalence of severe trachoma by 45.4%. This is the first study presenting evidence of an association between cattle and trachoma. On the basis of this study a strong recommendation is made to the Ministry of Health to control cattle pollution in rural areas as a major strategy to prevent blindness in Ethiopia.

Sociomedical Contributions to Trachoma Research and Intervention

Although the importance of human factors in the transmission and control of blinding trachoma has long been recognized, little sociomedical research has been undertaken on this disease. The trachoma literature contains considerable anecdotal information and a few reports relating to human behavioral, cultural, social, and economic factors, but systematic study in this area is needed. The potential range of sociomedical contributions to trachoma research is wide, including studies on the transmission of the disease, its consequences (especially blindness), and the planning, logistics, monitoring, and evaluation of intervention programs.

Transmission of chlamydiae by the housefly.

The ability of the housefly to carry viable Chlamydia trachomatis and to transmit a chlamydial ocular infection was studied under laboratory conditions. After feeding flies (Musca domestica) on suspensions of egg yolk sac infected with C. trachomatis serotypes A or B (responsible for hyperendemic trachoma) the agents were reisolated from flies' intestines for up to 6 hours and from their legs and/or proboscises for up to 2 hours. It was found that the viability of chlamydiae is dependent on the protective effect of yolk concentration in the original inoculum. Results of experiments with guinea-pig inclusion conjunctivitis as an animal model show that under laboratory conditions flies can readily transmit this chlamydial ocular infection from one animal to another. These results suggest that under field conditions flies can play an important role in the transmission of trachoma, particularly in areas with favourable conditions such as a large reservoir of infection among children with severe trachoma, copious eye discharge caused by trachoma and associated bacterial infections, a large fly population, and close proximity of children in large family groups.

A Study of Pannus Formation in the Cornea of Rabbits.

In the transmission of experimental trachoma to animals, perhaps the most significant and refractory difficulty is the complete lack of corneal involvement. Except in man where infection followed accidental or intentional transfer of trachomatous material. pannus formation has not accompanied folliculosis experimentally induced in a variety of animals. Since the appearance of cicatricial changes and pannus comprise the essential diagnostic differentiation between trachoma and folliculosis, the necessity is obvious for studying the conditions under which vascularization of the cornea is stimulated. While it is not yet clear that the data thus far obtained may be correlated eventually with pannus formation in trachoma, it is of interest that pannus may be evoked by various stimuli. From this point of view the experiments undertaken are here reported. The experiments have been done on rabbits; and because the results of a former study indicated that pannus may be a manifestation of bacterial hypersensitiveness, it was decided to study vascularization of the cornea as an allergic response. Rabbits have been sensitized to different bacteria; Staph. aureus, Bact. granulosis, Pneumococcus, diphtheroids and indifferent streptococci. Various methods for inducing hypersensitiveness of the cornea to bacteria were studied, but the most successful one was scarification of the cornea with one scratch reaching from below the sclero-corneal margin to the pupil, and then instilling into the conjunctival sac 2 drops of a young, actively growing culture. This treatment was repeated at weekly intervals.S. aureus proved to be the most effective sensitizing antigen, while B. granulosis was one of the least.

Direct Transmission of Human Trachoma to the Monkey

Direct Transmission of Human Trachoma to the Monkey

Direct Transmission of Human Trachoma to the Monkey

Direct Transmission of Human Trachoma to the Monkey

Transmission of Experimental Trachoma by Contact

Transmission of Experimental Trachoma by Contact

An Etiological Factor in Trachoma

This paper suggests a possible carrier or intermediary host concerned in the transmission of trachoma. It brings together certain facts regarding this disease that would be explained were the hypothesis accepted. It suggests possibilities in etiology.